JP4470629B2 - Lighting device - Google Patents

Description

  The present invention relates to a lighting device, and more particularly to a planar lighting device including a light guide plate that guides light from a light source and emits the light from an emission surface.

  Usually, a so-called backlight, which is an illumination light source used on the back surface of a transmissive LCD panel, uses a light guide plate made of a transparent resin in order to uniformly guide light from the light source to the LCD panel. As shown in FIG. 15, in the illumination device 14 in which the light source 12 is disposed on this type of light guide plate 10, the light incident on the light guide plate 10 from the light incident side end surface 11 of the light guide plate 10 is transmitted to the light guide plate 10. The light guide plate 10 travels along the direction of arrow F in the figure while totally reflecting the plane portion. FIG. 15 shows an example in which a linear light source is used as the light source 12, but the shape of the light source 12 is not limited to a linear shape, and may be, for example, a dot shape. Prisms 13 are provided in places on the plane portion of the light guide plate 10, and light hitting the prisms 13 is emitted upward from the light guide plate 10 according to the emission direction indicated by the arrow E in the figure.

  As shown in FIG. 16, a transmissive LCD panel 18 is disposed on the light guide plate 10 of the illumination device 14, and the light emitted from the light guide plate 10 according to the emission direction indicated by the arrow E in the drawing is transmitted. Is displayed.

  As a known example of the light guide plate 10 in which the prism 13 is provided on the back surface as shown in FIGS.

On the other hand, as an example of an illumination device that does not use the prism 13, there is a method of diffusing and emitting light by printing scattering dots on the surface of the light guide plate 10.
JP-A-5-264819

  However, it is difficult for such an illuminating device 14 to increase the ratio of the light incident on the light guide plate 10 from the light source 12 to the emitted light while making the light intensity in the emission surface 26 uniform, and the transmissive type There is a problem that light utilization efficiency (the ratio of light incident on the light guide plate 10 from the light source 12 that is converted into emitted light in a desired angle range as illumination light) when used as a backlight of the LCD panel 18 is low. is there.

  In particular, as the backlight of the LCD panel 18, it is desired to emit strong light in the normal direction of the emission surface 26, but it is extremely difficult to achieve this by using only the combination of the light source 12 and the light guide plate 10 in the prior art. In order to convert the light emitted from the light guide plate 10 into an appropriate light distribution, a method of inserting various optical films between the light guide plate 10 and the transmissive display element has also been proposed. Another problem arises that the thickness increases and the manufacturing cost increases.

  Further, when the prism 13 is used, the structure is relatively large, so that it is difficult to hide the arrangement pattern of the prism 13 during visual observation, the light guide plate 10 is thickened by the prism 13, There is a problem that the emission angle range and the emission light intensity cannot be freely controlled.

  Furthermore, when the light source 12 is installed on the light incident side end face 11 of the light guide plate 10, it is difficult to make the light intensity constant on the side close to the light source 12 and on the side far from the light source 12. In particular, in the case of a spot-like light source or an uneven light source, an average light guide direction (light guide through the light guide plate) is an average direction in which light travels from the light incident side end surface 11 to the end surface far from the light source 12. It is more difficult to increase both the uniformity of the distribution of the emitted light in the direction orthogonal to F and the light utilization efficiency.

  The present invention has been made in view of such circumstances, and its purpose is to increase the light use efficiency, to increase the uniformity of the emitted light intensity on the exit surface, and to make the angle range of the emitted light freely. An object of the present invention is to provide a lighting device having a simple configuration that can be controlled.

  In order to achieve the above object, the present invention takes the following measures.

  That is, the invention of claim 1 is a lighting device including a light source and a planar light guide plate that guides light incident from the light source and emits the guided light from the exit surface. And an emission optical element arranged on the emission surface or the surface opposite to the emission surface so that the arrangement density increases as the distance from the light incident side of the light guide plate increases, and the light guide plate on the surface where the emission optical element is arranged The diffusive optical element is arranged so that the arrangement density decreases as the distance from the light incident side increases.

  Therefore, the non-uniformity of the light distribution on the light incident side of the light guide plate (particularly the non-uniformity in the direction perpendicular to the average light guide direction) due to the size and number of the light sources, and the unevenness of the amount of light emitted from the light sources. While eliminating by diffusing by the optical element, it is compensated by the arrangement density of the optical elements for emission and reduced to the emitted light, reducing the amount of light guided in the light guide plate along the average light guide direction. Even along the light guide direction, the amount of light emitted from the light guide plate can be made uniform.

  At this time, the non-uniformity in the direction orthogonal to the average light guide direction is generally the largest immediately after the light from the light source is incident on the light guide plate, and once the light to be guided becomes uniform, it is uniform thereafter. Since it is easy to maintain the light guide state, it is most desirable to eliminate the non-uniformity near the light incident side of the light guide plate. In the invention of claim 1, sufficient uniformity is realized by increasing the arrangement density of the diffractive optical elements on the light incident side of the light guide plate, and the arrangement density is reduced as the uniformity increases. Thus, sufficient uniformity can be obtained over the entire light guide plate. Furthermore, it becomes possible to dispose the diffusing optical element and the emitting optical element without difficulty on the exit surface of the light guide plate or on the opposite surface, and high uniformity can be easily obtained.

  In addition, since the optical element for emission is composed of a diffraction grating, the structure is extremely small, and it can be easily formed in any area by microfabrication technology, etc., so the arrangement on the light guide plate is optimized. It is possible to construct a light guide plate having a very uniform emission light distribution.

  In addition, the angle range of the emitted light can be appropriately designed by the function of the diffraction grating, and a uniform illumination device having an emitted light distribution in the desired angle range can be realized with a small number of member configurations without necessarily using another optical film. It becomes possible. Moreover, since these optical effects are realized on a single surface on the light guide plate, it can be manufactured very easily while maintaining the positional relationship between the emission optical element and the diffusing optical element with high accuracy. .

  According to a second aspect of the present invention, in the illumination device of the first aspect of the present invention, a plurality of cells are arranged on a surface on which the emission optical element and the diffusive optical element are arranged, and the emission optical element and the diffusive optical element are: It is arranged in any one of a plurality of cells. Then, by adjusting the number and / or size of the cells in which the emission optical elements are arranged and the cells in which the diffusive optical elements are arranged, the arrangement density of the emission optical elements is increased as the distance from the light incident side increases. The density is increased, and the arrangement density of the diffusive optical elements is reduced as the distance from the light incident side increases.

  Therefore, the arrangement density of the emission optical element and / or the diffusive optical element at each position of the light guide plate can be easily optimized by setting the number of arranged cells and / or the size of the cells. And it becomes possible to implement | achieve an exact uniform emitted light distribution.

  According to a third aspect of the present invention, in the illumination device according to the second aspect of the present invention, the average light guide direction size of the light guided through the light guide plate of the cell in which the emission optical element is arranged is 5 μm or more and 100 μm or less. And

  Therefore, in the average light guide direction, the light emitted from the emission optical element can be expanded according to the size of the cell (the smaller the cell in the specific direction, the more the light expands in that direction), and as an illumination device The injection angle range can be adjusted. This is effective both when the diffraction grating constituting the emission optical element is a simple diffraction grating and when the diffraction grating has an action like a lens and has a function of spreading light. Furthermore, when the light incident on the light guide plate from the light source is white light, the spectral action of the diffraction grating can be made inconspicuous by the effect of spreading the light depending on the cell size, and the emitted light with a more uniform wavelength distribution Can be realized. If the size of the cell is 5 μm or more, the diffraction grating will exhibit a sufficient function, and if it is 100 μm or less, the cell should be arranged so that it can be felt sufficiently even when the exit surface is visually observed. Can do.

  According to a fourth aspect of the present invention, in the illumination device according to the second or third aspect of the present invention, a direction orthogonal to an average light guide direction of light guided through the light guide plate of the cell in which the diffusive optical element is disposed. Is 1 μm or more and 100 μm or less.

  Therefore, in the direction orthogonal to the average light guide direction, the light emitted from the diffusive optical element can be expanded according to the size of the cell, and the light quantity distribution in the direction orthogonal to the average light guide direction in the light guide plate is obtained. It can be made uniform. This means that in addition to the diffusing function of the diffusing optical element itself, the light is further diffused, so that further uniformization can be achieved. The smaller the cell size, the greater the diffusion effect due to the cell size, and if substantially 1 μm or more, a diffusive optical element can be formed inside, and if it is 100 μm or less, the diffusion effect is sufficient, The cells can be arranged so as to be sufficiently uniform even when the exit surface is visually observed.

  According to a fifth aspect of the present invention, in the illumination device of the first aspect, the arrangement density of the emitting optical elements increases as the distance from the light incident side increases, and the arrangement density of the diffusive optical elements decreases as the distance from the light incident side increases. As described above, the first area where the emission optical element is arranged and the second area where the diffusive optical element is arranged alternately on the surface where the emission optical element and the diffusive optical element are arranged. Place with.

  Accordingly, it is easy to realize that the arrangement density increases as the emitting optical element moves away from the light incident side of the light guide plate, and the arrangement density decreases as the diffusing optical element moves away from the light incident side of the light guide plate. A uniform emission light distribution within the emission surface of the light guide plate can be obtained very easily and reliably.

  According to a sixth aspect of the present invention, in the illumination device of the first aspect, the arrangement density of the emitting optical elements increases as the distance from the light incident side increases, and the arrangement density of the diffusive optical elements decreases as the distance from the light incident side increases. As described above, the emission optical element and the diffusive optical element are arranged so as to intervene on the surface on which the emission optical element and the diffusive optical element are arranged.

  Therefore, the emission optical element and the diffusive optical element are easily included in the small area, and the uniformity of the emitted light between the small areas on the emission surface of the light guide plate is further improved.

  According to a seventh aspect of the present invention, in the illumination device according to any one of the first to sixth aspects of the present invention, the emission optical element has a direction of light guided through the light guide plate and a normal line to the emission surface. The diffusing optical element is bent so as to approach the direction, and diffuses the light guided in the light guide plate in a direction orthogonal to the average light guide direction of the light guided in the light guide plate.

  Therefore, while suppressing the inadvertent emission of the light to be guided out of the light guide plate by the diffusive optical element, it is orthogonal to the average light guide direction due to the size and number of light sources and the unevenness of the amount of light emitted from the light sources. In addition, the non-uniformity of the light amount distribution in the direction to be emitted can be reliably eliminated in the diffusive optical element, and in addition, the conversion from the light guide plate to the emitted light can be appropriately and reliably realized by the emitting optical element.

  An eighth aspect of the present invention is the illumination device according to any one of the first to seventh aspects, wherein the emission optical element and the diffusive optical element are formed by a relief structure.

  At this time, it is preferable that a surface relief type diffraction grating is used as the emitting optical element, and a concavo-convex pattern arranged at random is used as the diffusing optical element, which can be easily realized. In particular, as the latter, linear unevenness parallel to the average light guide direction F is randomly arranged to diffuse light in a direction orthogonal to the average light guide direction F, and to guide light in the direction of the average light guide direction F. Both state invariance can be achieved and it is optimal.

  Therefore, since both the emission optical element and the diffusive optical element formed on the emission surface of the light guide plate or the opposite surface thereof have a minute relief structure, the above-described effects can be obtained by molding the corresponding surface of the light guide plate once. The light guide plate can be formed, and the lighting device can be configured simply and inexpensively. Moreover, if the optical element for injection and the diffusive optical element are accurately arranged and formed on the relief original plate, a light guide plate on which both optical elements are accurately arranged can be extremely stably and inexpensively produced as a replica of the relief. It is possible to obtain an illumination device that can be produced and has little variation between products.

  As described above, according to the present invention, the illumination device can increase the light utilization efficiency, increase the uniformity of the emitted light intensity on the exit surface, and freely control the angle range of the emitted light. Can be realized with a simple configuration.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a perspective view showing a configuration example of a lighting apparatus according to the first embodiment of the present invention.

  That is, the illuminating device 16 according to the present embodiment includes the light source 12 and the planar light guide plate 10 that guides the light incident from the light source 12 and emits the guided light from the exit surface 26. Yes. An emission optical element 38 and a diffusive optical element 39 are provided on the opposing surface 27 of the emission surface 26.

  FIG. 2 is a plan view showing an arrangement example of the emission optical element and the diffusive optical element in the illumination device according to the embodiment. As shown in FIG. 2, the emission optical element 38 is formed of, for example, a diffraction grating, and is arranged on the opposing surface 27 of the emission surface 26 so that the arrangement density increases as the distance from the light incident side end surface 11 of the light guide plate 10 increases. is doing. Further, the diffusing optical element 39 is disposed on the opposite surface 27 that is the same surface on which the emission optical element 38 is disposed so that the disposition density decreases as the distance from the light incident side end surface 11 of the light guide plate 10 increases. .

  FIG. 1 shows an example in which the emission optical element 38 and the diffusive optical element 39 are arranged on the opposite surface 27 of the emission surface 26. However, the emission optical element 38 and the diffusive optical element 39 are arranged on the emission surface 26. Instead of being arranged on the opposite surface 27, it may be arranged on the exit surface 26.

  The illuminating device 16 according to the present embodiment having such a configuration guides light incident from the light source 12 by the light guide plate 10 and diffuses the guided light by the diffusive optical element 39. While eliminating the non-uniformity of the light amount distribution on the light incident side end face 11 side of the light guide plate 10 due to the unevenness of the emitted light amount from the light source 12 (particularly the non-uniformity in the direction R perpendicular to the average light guide direction F), A decrease in the amount of emitted light due to a decrease in the amount of light guided through the light guide plate 10 along the average light guide direction F is compensated by the arrangement density of the emission optical elements 38. As a result, light is uniformly emitted within the emission surface 26.

  At this time, since the non-uniformity of the light quantity distribution is gradually eliminated as the distance from the light incident side end face 11 is increased, the diffusive optical element 39 can be sufficiently uniformed even if the distance from the light incident side end face 11 is decreased. It is.

  Further, since the emission optical element 38 is composed of a diffraction grating, the structure is extremely minute and can be easily formed in an arbitrary region by a fine processing technique or the like. Can be optimized. Therefore, by further finely arranging the arrangement structure as shown in FIG. 2, it is possible to configure the light guide plate 10 having a very uniform emission light distribution.

  In general, the light guide plate 10 in which the optical elements for emission are uniformly arranged has a higher intensity of light emission toward the light incident side end face 11 side, and the intensity of the emitted light becomes smaller as the distance from the light source 12 approaches the opposite end face. For this reason, when the diffraction efficiency of the diffraction grating constituting the emission optical element 38 is constant, as the distance from the light incident side end face 11 side increases in the average light guide direction F of the light guide plate 10, as shown in FIG. By increasing the arrangement density of the emission optical elements 38, the ratio of light emitted from the light guide plate 10 is small on the light incident side end face 11 side where the light intensity is strong, and the emission ratio increases as the distance from the light incident side end face 11 side increases. It is possible to emit light with uniform intensity over the entire exit surface 26 of the light guide plate 10.

  Further, the angle range of the emitted light can be appropriately designed by the function of the diffraction grating constituting the emission optical element 38, and a uniform illumination device having an emission light distribution in a desired angle range without necessarily using another optical film or the like. Can be realized.

  Here, when the linear light source 12 arranged substantially parallel to the light incident side end surface 11 is used as the light source 12, the average light guide direction F in the light guide plate 10 is a direction substantially orthogonal to the light incident side end surface 11. Become. In addition, as shown in FIG. 3, when a light source 12a such as a dotted LED arranged on the light incident side end face 11 side is used as the light source, light is guided in a radial direction centered on the light source 12a. When averaged over the entire light guide plate 10, the direction substantially perpendicular to the light incident side end face 11 is the average light guide direction F as in the case of the linear light source 12.

  FIG. 4 is a partial plan view showing the function of the diffusive optical element in the illumination device according to the embodiment. This figure shows a state in which the diffusing optical element 39 diffuses the light being guided in a plane parallel to the exit surface 26 in the illumination device 16. At this time, if the light is diffused strongly in the direction R perpendicular to the average light guide direction F, the unevenness in brightness and the like originating from the position where the light source 12 is disposed can be eliminated, and the distribution of light guided through the light guide plate 10 can be made uniform. In addition, since the light can be diffused without inadvertently emitting light from the light guide plate 10 by hardly affecting the light guide direction, the light use efficiency can be improved.

  FIG. 5 is a side view showing the function of the emission optical element in the illumination apparatus according to the embodiment. This figure shows a state in which the emission optical element 38 in the illumination device 16 of FIG. 1 emits light in the light guide plate 10. As shown in FIG. 6, when the illumination device 16 according to the present embodiment is used as the backlight of the transmissive LCD panel 18, the emission optical element 38 emits the light being guided. Although it is desirable to convert the light to be emitted in an emission direction E substantially perpendicular to the surface 26, this can be easily realized by using a diffraction grating as the emission optical element 38.

  Furthermore, it is possible to set the angle range of the emitted light as appropriate by the function of the diffraction grating, and to realize illumination light having an optimal angular distribution as a display without using any other optical film. Can do.

  FIG. 5 shows an example in which the emission optical element 38 and the diffusive optical element 39 are arranged on the opposite surface 27 of the emission surface 26. In this case, it is desirable to use a reflective diffraction grating. For example, a relief type diffraction grating may be formed only on the surface of the light guide plate, or a metal reflection film may be provided on the surface. On the other hand, when the emission optical element 38 and the diffusive optical element 39 are arranged on the emission surface 26, the same effect can be obtained if the diffraction grating is a transmission type.

  In addition, when a relief type diffraction grating is used as the diffraction grating of the emission optical element 38, it is easy to design a pattern and to improve the efficiency. At this time, since the structure of the relief type diffraction grating is typically about 0.1 to 1 μm, it is possible to realize the light guide plate 10 that can be regarded as a substantially flat surface with no unnecessary protrusions. That is, the illumination device 16 can be thinned.

Of the light guided through the light guide plate 10, the light incident on the emission optical element 38 generates diffracted light by the diffraction grating, but the normal main diffracted light is first-order diffracted light. In the minute region of the diffraction grating, the relationship between the grating pitch d of the diffraction grating and the emission angle (diffraction angle) θR of the first-order diffracted light is expressed by the following equation (1).

Where m is the diffraction order, λ is the wavelength of light, and θi is the regular reflection angle (when the diffraction grating acts during reflection).

  In order to convert the light traveling in the light guide plate 10 in the average light guide direction F into the emitted light, the diffraction grating that works most effectively has a grating vector v along the average light guide direction F. That is, by making the direction of the grating vector v and the average light guide direction F substantially the same or different from each other by 180 °, and appropriately setting the grating pitch d, the light traveling in the average light guide direction F while being totally reflected is reflected by the diffraction grating. Is diffracted at an angle of θR and exits from the exit surface 26 of the light guide plate 10 outside the total reflection condition. In particular, when θR to 0 °, illumination light is emitted almost perpendicularly to the surface of the light guide plate 10 and is most preferable as illumination light for a transmissive display.

  The diffraction grating constituting the emission optical element 38 not only emits the light guided through the light guide plate 10 as diffracted light, but can also control how the diffracted light spreads (emission angle range). is there. Specifically, the pattern of the linear diffraction grating 40 as shown in the plan view in FIG. 7A and the sectional view in FIG. 7B is guided along the average light guide direction F. It only has the function of bending light. Further, in the pattern of the curved diffraction grating 41 as shown in the plan view of FIG. 8A and the cross-sectional view of FIG. 8B, the range of the diffracted light to be emitted can be arbitrarily designed by the pattern. 7 and 8, x is a direction matching the average lattice vector v, y is a direction orthogonal to x, and h is a lattice height.

  Here, the diffraction grating pattern on the light guide plate 10 is, as shown in FIGS. 7 and 8, when the average light guide direction F and the average grating vector direction v coincide with each other or are different by 180 °, It can be set as the structure which acts effectively with respect to the light which satisfy | fills a total reflection condition. That is, the direction of the emitted light can be greatly different from the light being guided, and the light can be reliably emitted from the light guide plate 10.

  Furthermore, when the emission optical element 38 and the diffusive optical element 39 are configured by a relief structure, they can be integrally molded with the light guide plate 10 and can be molded on a single surface. It can be manufactured. At this time, the arrangement positions of the injection optical element 38 and the diffusive optical element 39 are determined at the time of production of the original, and the arrangement positions are always stably reproduced at the time of mass production by copying (molding) the original. An accurate light guide plate can be easily manufactured.

  As described above, the light emitted from the illuminating device 16 according to the embodiment of the present invention has a controlled emission angle range, can achieve a uniform distribution in the emission surface 26, and is extra for other optical sheets and the like. Therefore, it is possible to provide a lighting device that is highly efficient in using light, is thin, and inexpensive.

  In addition, the light guide plate 10 may have a configuration in which the thickness is made constant as well as a case where the thickness gradually decreases as the light guide plate 10 moves along the average light guide direction F as shown in FIG.

  Further, as shown in FIG. 9, by disposing the reflector 32 so as to cover the surface of the opposing surface 27 of the light guide plate 10, the leaked light from the opposing surface 27 is reflected again to the light guide plate 10 side and reused. And the light utilization efficiency can be further enhanced.

(Second Embodiment)
The illuminating device according to the second embodiment of the present invention is a modification of the illuminating device according to the first embodiment, and a plurality of illuminating devices are provided on the surface on which the emission optical element 38 and the diffusing optical element 39 are arranged. In addition, the emission optical element 38 and the diffusing optical element 39 are arranged in any one of the plurality of cells. Then, by adjusting the number or size of the cells in which the emission optical elements 38 are arranged and the cells in which the diffusive optical elements 39 are arranged, the arrangement density of the emission optical elements 38 is changed to the light incident side end face 11. The arrangement density of the diffusive optical elements 39 is reduced as the distance from the light incident side end face 11 increases.

  An example is shown in FIG. As shown in FIG. 10, a large number of emission optical elements 38 and diffusive optical elements 39 are arranged on the emission surface 26 of the light guide plate 10 or the opposing surface 27 so as to interlace with each other. Here, each of the emission optical elements 38 and each of the diffusive optical elements 39 corresponds to a cell. Then, the number of cells including the diffusive optical element 39 is increased toward the light incident side end face 11 side, and from there to decrease toward the downstream side in the average light guide direction F. In addition, the number of cells formed of the emission optical elements 38 is decreased toward the light incident side end face 11 side, and is increased toward the downstream side in the average light guide direction F therefrom.

  Another example is shown in FIG. As shown in FIG. 11, a large number of emission optical elements 38 and diffusive optical elements 39 are arranged on the emission surface 26 of the light guide plate 10 or its opposite surface 27 so as to interlace with each other. Here, each of the emission optical elements 38 and each of the diffusive optical elements 39 corresponds to a cell. Then, the size of the cell composed of the diffusive optical element 39 is made larger toward the light incident side end face 11 side and smaller from there toward the downstream side in the average light guide direction F. In addition, the size of the cell composed of the emission optical element 38 is set to be smaller toward the light incident side end face 11 side and to be larger toward the downstream side of the average light guide direction F therefrom.

  Yet another example is shown in FIG. As shown in FIG. 12, a diffusion element region 42 for disposing a diffusive optical element 39 and an emission element for disposing an emission optical element 38 on the emission surface 26 of the light guide plate 10 or the opposing surface 27 thereof. A working area 43 is provided. The diffusion element region 42 has a comb blade shape such that the cutting edge becomes thinner toward the average light guide direction F. On the surface where the diffusion element region 42 is disposed, the regions other than the diffusion element region 42 are It is set as the emission element region 43. Accordingly, the diffusive optical element 39 is disposed in the diffusion element region 42 on the surface where the diffusion element regions 42 and the emission element regions 43 are alternately arranged in this manner, and the emission optical element 38 is disposed in the emission element region 43. By doing so, the arrangement density of the emitting optical elements 38 increases as the distance from the light incident side end face 11 increases, and the arrangement density of the diffusive optical elements 39 decreases as the distance from the light incident side end face 11 increases.

  By doing so, it is possible to easily optimize the arrangement density of the emission optical elements 38 and the diffusive optical elements 39 at each position of the light guide plate 10, and the same effect as in the first embodiment. It is possible to realize a uniform emitted light distribution more easily and accurately while having

  In particular, as shown in FIG. 12, the diffusing element region 42 and the emitting element region 43 are alternately arranged so that the emitting optical element 38 is guided from the light incident side end face 11 of the light guide plate 10 to the average light guide. It is possible to easily realize that the arrangement density is increased as it is separated along the direction F, and the arrangement density is reduced as the diffusible optical element 39 is separated from the light incident side end face 11 along the average light guide direction F. A uniform emission light distribution within the emission surface 26 of the light guide plate 10 can be obtained very easily and reliably.

  On the other hand, as shown in FIGS. 10 and 11, the emission optical element 38 and the diffusing optical element 39 are arranged on the light guide plate 10 so that the emission optical element 38 and the emission optical element 38 are arranged in a small area. The diffusive optical element 39 is included, and the uniformity of the emitted light between the small areas on the emission surface 26 is further improved, that is, the uniformity of the entire light guide plate 10 is guaranteed.

  Here, in FIGS. 10, 11, and 12, the outer shape of the cell is a rectangular shape as shown in an enlarged view in FIG. 13 (a), but the outer shape of the cell is limited to a rectangular shape. It is not a thing, and elliptical shape as shown in FIG.13 (b) and circular shape although not shown in figure may be sufficient. Moreover, all the cells arranged on the same light guide plate 10 may have the same shape, or a rectangular shape, a circular shape, and an elliptical shape may be mixed. As an optimal design example, the cells of the diffusive optical element 39 are long in the average light guide direction F and have a short shape in the direction F orthogonal thereto, and the cells of the emission optical element 38 are short in the average light guide direction F. If it has a long shape in the direction R orthogonal thereto, each optical function can be supported by the diffraction effect due to the cell shape.

  Further, the size of each cell is set to 100 μm or less in the present embodiment because the appearance is impaired if the size is large enough to be observed with the naked eye. A size of 100 μm or less is preferable because it cannot be observed with the naked eye and does not impair the appearance.

  On the other hand, the diffraction effect due to the cell shape will be described with reference to FIG. 14 showing the relationship between the aperture size by Fraunhofer diffraction and the spread width of the diffracted light.

The light intensity distribution by Fraunhofer diffraction of a rectangular opening as shown in FIG. 13A can be calculated by the following formula, and depends on the size of the opening in the direction I (x, y) orthogonal to the sides of the rectangular opening. It can be seen that the light spreads.

At this time, λ is the wavelength of light, and R is the distance from the opening to the surface where the light intensity is observed in Dx and Dy, respectively, in two directions (x direction and y direction) orthogonal to the size of the rectangular opening. Since A is a value that does not depend on the size of the rectangular opening, it can be treated as a constant here. Where the sinc function is

It is.

  Therefore, in the present invention, since the size of the cell corresponds to the opening, it is possible to control how the first-order diffracted light spreads in the x direction and the y direction according to the size of the cell. In particular, in the case of the emission optical element 38, the first-order diffracted light by the diffraction grating has such a spread, and the spread of the emitted light in a specific direction can be controlled also by the size of the cell. Further, in the case of the diffusive optical element 39, the diffused light has such a spread, so that it can be designed to further enhance the diffusibility in a specific direction.

  Specifically, assuming that the x direction is the average light guide direction F, when the cell size in the x direction is 100 μm, the spread of the diffracted light (diffracted light of the diffracted light at a position 300 mm away from the wavelength λ of 500 nm). The width between the places where the intensity first becomes 0 around the peak is about 3 mm. On the other hand, when the cell size in the x direction is 5 μm, the spread of the diffracted light is about 60 mm. When the cell size in the x direction is 10 μm, the spread of the diffracted light is about 30 mm. When these are graphed under the above conditions, they are as shown in FIG.

  Therefore, if the cell size is in the range of 5 μm or more and 100 μm or less, the spread of the diffracted light can be controlled over a practically sufficient range from 60 mm to 3 mm. Further, if the cell size is 5 μm or less, the spread can be further increased. In the case of the emission optical element 38, it is desirable to be 5 μm or more in order to effectively function the diffraction grating formed inside the cell, but the diffusive optical element 39 is formed in a granular shape or a concavo-convex pattern. Accordingly, the diffusibility depending on the cell size may be positively utilized by reducing the thickness to 1 μm.

  From the above, the spread width of the diffracted light can be controlled by the length in each direction of the cell, and the method of spreading the illumination light emitted from the illumination device according to the present embodiment can be appropriately designed. In particular, when white light is emitted as illumination light, the degree to which the diffracted light is dispersed by the diffraction grating of the emission optical element 38 can be obtained by the above equation (1), but the cell length Dx in the grating vector direction v is set as follows. By making it sufficiently small, the spread width of the diffracted light can be increased and the influence of spectroscopy can be suppressed.

  In addition, by making the outer shape of the cells the same on the light guide plate 10, it is possible to make the diffracted light spread more uniform. Alternatively, the way in which the diffracted light spreads depending on the cell shape can be arbitrarily controlled by cells having different sizes and shapes and cells having different arrangement directions on the surface of the light guide plate 10.

  For example, by making the shape of the cell a rectangle, the diffracted light can be spread only in the direction orthogonal to each side of the rectangle, and the spreading method can be controlled by the size of the rectangle in the direction. Accordingly, it is possible to freely design how the emitted light spreads in two directions. In general, it is desirable to arrange a rectangle so that a pair of sides are orthogonal to the average light guide direction F of the light guide plate 10 and to control how the emitted light spreads in the direction orthogonal to each side. . As a result, the spread method of the emitted light in the average light guide direction F and the direction R orthogonal thereto is set independently, and the direction and intensity of diffusion are appropriately controlled, the angle range of the emitted light is controlled, and diffraction is performed. It is possible to cancel the wavelength dispersion effect due to the grating.

  Further, by making the shape of the cell circular or elliptical, it is possible to realize emitted light that spreads in all directions. At that time, the spread of the emitted light can be controlled by the size of the cell. In the case of an ellipse, the way in which the diffracted light spreads in the direction perpendicular to the major axis and the minor axis can be controlled by the size in that direction. Accordingly, it is possible to freely design how the emitted light spreads in two directions. In general, it is desirable to arrange the light guide plate 10 so that one axis is perpendicular to the average light guide direction F of the light guide plate 10 and to control how the emitted light spreads in the direction perpendicular to each side. As a result, the spread method of the emitted light in the average light guide direction F and the direction R orthogonal thereto is set independently, and the direction and intensity of diffusion are appropriately controlled, the angle range of the emitted light is controlled, and diffraction is performed. The wavelength dispersion effect due to the grating can be minimized.

  Further, when the cell arrangement interval is set to 100 μm or less, the resolution becomes less than the human eye under general observation conditions. Even when the exit surface 26 of such an illuminating device is visually observed, the size of the cell is sufficiently small. Since a sufficient number of cells can be arranged per unit area, it can be observed as a surface that emits uniform emitted light.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, this invention is not limited to this structure. Within the scope of the invented technical idea of the scope of claims, a person skilled in the art can conceive of various changes and modifications. The technical scope of the present invention is also applicable to these changes and modifications. It is understood that it belongs to.

The perspective view which shows the structural example of the illuminating device which concerns on the 1st Embodiment of this invention. The top view which showed the example of arrangement | positioning of the optical element for emission in the illuminating device which concerns on the embodiment, and a diffusive optical element. The schematic diagram which shows the light guide state of the light radiated | emitted from the point light source. The fragmentary top view which showed the function of the diffusable optical element in the illuminating device which concerns on the embodiment. The side view which showed the function of the optical element for injection | emission in the illuminating device based on the embodiment. The conceptual diagram of the transmission type LCD panel which used the illuminating device which concerns on the form as a backlight. The top view and sectional drawing of a linear diffraction grating pattern. The top view and sectional drawing of a curved diffraction grating pattern. The perspective view which shows the structural example which uses the reflecting plate for the back surface of the illuminating device which concerns on the embodiment. The top view which shows an example of the illuminating device which has arrange | positioned many optical elements for injection | emission and a diffusible optical element mutually intermingled. The top view which shows another example of the illuminating device which has arrange | positioned many optical elements for injection | emission and a diffusible optical element mutually intermingled. The figure which shows an example of the illuminating device provided with the surface where the area | region for spreading | diffusion elements and the area | region for injection | emission elements entered alternately. The top view which shows the example of a shape of a cell. The figure which shows the relationship between the opening size by Fraunhofer diffraction, and the breadth of diffracted light. The perspective view which shows the illuminating device with which the light guide by a prior art is applied. The perspective view which shows the display apparatus with which the illuminating device shown in FIG. 15 is applied.

Explanation of symbols

  E ... Ejection direction, F ... Average light guide direction, d ... Lattice pitch, v ... Lattice vector direction, 10 ... Light guide plate, 11 ... Light incident side end face, 12 ... Light source, 13 ... Prism, 14, 16 ... Illumination device, DESCRIPTION OF SYMBOLS 18 ... LCD panel, 24 ... Display apparatus, 26 ... Ejection surface, 27 ... Opposite surface, 32 ... Reflector, 38 ... Optical element for emission, 39 ... Diffusing optical element, 40, 41 ... Diffraction grating, 42 ... Diffusing element Area 43 for injection element

Claims (8)

In a lighting device including a light source and a planar light guide plate that guides light incident from the light source and emits the guided light from an exit surface.
An emission optical element that is configured of a diffraction grating and is arranged on the emission surface or the surface opposite to the emission surface so that the arrangement density increases as the distance from the light incident side of the light guide plate increases.
An illuminating device comprising: a diffusive optical element disposed on a surface on which the emission optical element is disposed so that the arrangement density decreases as the distance from the light incident side of the light guide plate increases. The lighting device according to claim 1.
A plurality of cells are arranged on a surface on which the emission optical element and the diffusive optical element are arranged, and the emission optical element and the diffusive optical element are arranged in any of the plurality of cells. And adjusting the arrangement number and / or size of the cell in which the emission optical element is arranged and the cell in which the diffusive optical element is arranged, thereby adjusting the arrangement density of the emission optical element to the light incidence. An illuminating device in which the arrangement density of the diffusive optical elements increases as the distance from the side increases, and decreases as the distance from the light incident side increases. The lighting device according to claim 2,
An illumination device in which a size of an average light guide direction of light guided through the light guide plate of the cell in which the emission optical element is arranged is 5 μm or more and 100 μm or less. In the illuminating device of Claim 2 or Claim 3,
A lighting device in which a size of a cell in which the diffusible optical element is arranged is 1 μm or more and 100 μm or less in a direction orthogonal to an average light guide direction of light guided in the light guide plate. The lighting device according to claim 1.
The emission optical element and the diffusive optical element so that the arrangement density of the emission optical element increases as the distance from the light incident side increases, and the arrangement density of the diffusive optical element decreases as the distance from the light incident side increases. A lighting device in which the first area where the emission optical element is arranged and the second area where the diffusive optical element is arranged are alternately arranged on the surface where is arranged. The lighting device according to claim 1.
The emission optical element and the diffusive optical element so that the arrangement density of the emission optical element increases as the distance from the light incident side increases, and the arrangement density of the diffusive optical element decreases as the distance from the light incident side increases. An illumination device in which the emission optical element and the diffusive optical element are arranged so as to be mixed with each other on the surface on which is disposed. In the illuminating device of any one of Claims 1 thru | or 6,
The emission optical element is bent so that the direction of light guided in the light guide plate is close to a normal direction to the emission surface, and the diffusive optical element is guided in the light guide plate. An illumination device configured to diffuse light in a direction orthogonal to an average light guide direction of light guided in the light guide plate. The illumination device according to any one of claims 1 to 7,
An illumination device in which the emission optical element and the diffusive optical element are formed by a relief structure.

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